Mass-separated Focused Ion Beams for Self-Organized Surface Patterning

Heavy mon- and polyatomic ions (Au or Bi) from mass-separated FIB working with LMAIS can cause localized melting at the ion impact point due to the enhanced energy density in the collision cascade [1,2]. The formation of high aspect ratio, hexagonal dot patterns on Ge, Si or GaAs after high fluence, normal incidence irradiation choosing a suited combination of energy density deposition and substrate temperature, which facilitated transient melting of the ion collision cascade volume could be demonstrated [2-5]. In this study the universality of this ion impact-melting-induced, self-organized pattern formation is expanded to the compound semiconductor GaSb under Aunm+ ion irradiation with various conditions in particular, ion species, fluence, energy/atom, temperature and angle of incidence. Calculations of the needed melting energies per atom (Emelt) for different materials show, that GaSb is a preferring candidate for a successful surface patterning by mon- and polyatomic heavy ions whereas i.e. the surface of SiC remains stable under the given conditions. Furthermore the surface modification behavior under Au and Bi heavy ion impact should be compared. HR-SEM, AFM and EDX analysis of irradiated surfaces reveal that for compound semiconductors, additional superstructures are evolving on top of the regular semiconductor dot patterns, indicating superposition of a second dominant driving force for pattern self-organization.

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[2] L. Bischoff, K.-H. Heinig, B. Schmidt, S. Facsko, and W. Pilz, Self-organization of Ge nanopattern under erosion with heavy Bi monomer and cluster ions, Nucl. Instr. and Meth. B 272 (2012) 198.
[3] R. Böttger, L. Bischoff, K.-H. Heinig, W. Pilz and B. Schmidt, From sponge to dot arrays on (100)Ge by increasing the energy of ion impacts, Journal of Vacuum Science and Technology B 30 (2012) 06FF12.
[4] R. Böttger, K-.H Heinig, L. Bischoff, B. Liedke, R. Hübner, and W. Pilz,
Silicon nanodot formation and self-ordering under bombardment with heavy Bi3 ions, physica status solidi – Rapid Research Letters 7 (2013) 501.
[5] L. Bischoff, R. Böttger, K.-H. Heinig, S. Facsko, and W. Pilz, Surface patterning of GaAs under irradiation with very heavy polyatomic Au ions, Applied Surface Science 310 (2014) 154.